開水路粗度急変部における流れの遷移と流砂機構に関する研究

1.在推移质动平衡条件下，对包括光滑固定床在内的各类护床工程下游河段进行了局部冲刷试验。讨论了三种护底工程冲刷坑剖面及其最大深度随时间的变化规律，并与静平衡条件下的冲刷坑深度进行了比较。在冲刷过程的不同阶段，还测量了流速分布、床面剪应力和冲刷床上的压力等水流特性。冲刷过程可以通过沿最大冲刷剖面和非平衡推移质函数测得的床面剪应力分布来模拟，特别是在冲刷初期。在兵库县曼甘吉河下游的一段空心方块河段进行了冲刷剖面的现场测量，观测到的冲刷剖面和流速分布与试验测量的结果基本一致。对侧壁粗糙度由光滑突变为粗糙的明渠水流的水面线和湍动结构进行了实验研究。结果表明，水流的转变主要取决于床面坡度，可分为三种形态。在糙率变化后的下游河段，流速和紊动特性的分布随着内边界层的发展而变化，类似于底部粗糙度突变的情况。

1. Experiments of local scour in downstream reaches of various types of bed protection works including smooth fixed bed were carried out under dynamical equilibrium conditions of bed load. Variations of scour holes profiles and their maximum depths with time were discussed on three types of bed protection works, and compared with those under a static equilibrium condition. Flow characteristics, such as, velocity distributions, bed shear stress and pressure on the scoured bed were also measured at several stages of scour process. The scour processes could be simulated by the case of bed shear stress distributions measured along the maximum scour profile and non-equilibrium bed load functions, especially in the early stage of the scour.2. Field measurement of scour profiles were carried out at a downstream reach of hollow-squared blocks in the Manganji River in Hyogo prefecture, and the observed scour profiles and velocity distributions proved to be similar to those measured in the experiments.3. Water surface profiles and turbulent structures of open channel flows produced by sudden change in side-wall roughness from smooth to rough were discussed experimentally. The transition of flow was found to mainly depend on the bed slope and classified into three patterns. In the downstream reach after the roughness change, distributions of the velocity and turbulence property vary with development of the internal boundary layer similar to those by sudden change in bottom roughness.